MATERIALS AND METHODS

The animals used in this study were twenty, 50 day-old, male ICR rats (Nihon Crea). They had been bred with solid feed and tap water for one week after purchase. After surgery, they had been bred with solid and soft feed. Surgery was performed on 15 rats to cut the masseter muscle, with the remaining 5 rats used as controls. After they had been anaesthetized with sodium pentobarbitone (35 mg/Kg administered interperitoneally), surgery was performed as follows: about 4 mm deep tendon and muscle fibers that were attached to the deep region of the right mandible, were severed while paying careful attention to avoid damaging the nerves and blood vessels(Fig.1). The skin was then immediately sutured. The 15 rats were divided into 3 groups of 5 rats each and thoracotomy under general anesthesia on performed separate groups on days 3,7 and 14 after surgery. After inserting a cannula into the left ventricle and perfused with physiological saline solution for a short period of time, fixative ( 1% paraformaldehyde and 1.5% glutaraldehyde in 0.05M phosphate buffer pH: 7.3 ) was perfused. The mandible was then immediately removed, fixed in the same fixative over night at 4C (celcius), and decalcified using EDTA ( pH: 7.4 ) at 4C. After cleaning the decalcified sample in 0.1 M phosphate buffer, frontal-plane slices about 3 mm thick were cut. According to the conventional method, slices were then embedded in paraffin, continuous frontal-plane sections about 10 um thick cut, and sections stained using Azan stains.